Theory of Network Communication

The goal of this lecture is to give an introduction to the state of the art in the theory of network communication. It is a widely accepted fact that algorithmic advances in the area of computer science are only useful to society if they are based on models that truthfully reflect the restrictions and requirements of the corresponding applications. This is certainly also true for network communication. For example, in general any infrastructure connecting processing units with each other may be called a network, but certain infrastructures such as a dedicated line between every pair of nodes are certainly unrealistic, because they are too expensive to build. Thus, messages may have to traverse several units to reach their destination, causing (among other problems) route selection and scheduling problems. Also, we will not just study network communication out of context, but we will also look at various topics that require or support efficient network communication such as distributed data management or design strategies for overlay networks. In fact, during the last two years the course has made a transition from a mere networking course to a course in which the principles behind efficient networking are used to develop efficient distributed algorithms and data structures. Therefore, it should come as no surprise that this lecture will mostly be concerned about distributed computing instead of just networks. Before going into details, let us first give an overview of this section. We start with some philosophical thoughts about distributed computing. They can be safely skipped if the reader is not interested in the motivation behind the distributed computing paradigm used in this course. Also, the views should not be seen as the ultimate truth but should be looked at from a critical angle. This is followed by an introduction to the spheres framework, a framework that we will use to argue about protocols and distributed algorithms and data structures. Finally, an introduction to the E language will be given, which will be used for implementations in the course.